Life predicting method for rolling bearing, life predicting device, rolling bearing selecting device using life predicting device, program and environment coefficient determining method

ABSTRACT

To predict a correction rated life at high accuracy. A life predicting device executes step S 1 , step S 2 , step S 4  for inputting specification information including a basic dynamic rated load C and basic static rated load C 0 , step  5  for computing a dynamic equivalent load P based on the specification information. step S 3  for setting a reliability factor a 1 , step S 7  and step S 8  for determining a contact ellipse area S, step S 9  for inputting a foreign substance purchasing diameter d debris  (“debris” means “foreign substance”), step  10  for determining a standardized foreign substance diameter (d debris /√ S), step S 11  for setting a life correction coefficient a xyz  based on the standardized foreign substance diameter, and step S 6  and step S 12  for calculating a correction rated life L nm  based on the reliability coefficient, the life correction coefficient, the basic dynamic rated load and the dynamic equivalent load and the like.

BACKGROUND OF THE INVENTION

The present invention concerns a life predicting method for a rollingbearing, a life predicting device, a rolling bearing selecting deviceusing the life predicting device, a program therefor and an environmentcoefficient determining method.

A basic rated life L₁₀ of a rolling bearing is defined in JIS B 1518:1992 and, usually, a calculation formula as shown in the followingformula (1) is used.L ₁₀=(C/P)^(p)  (1)in which C represents a basic dynamic rated load of a rolling bearingand P represents a dynamic equivalent load exerting on the bearing.Further, p represents a load index which is set at p=3 in the case of aball bearing and p=10/3 in the case of a roller bearing. The basic ratedlife L₁₀ is defined for a case at a reliability of 90%, using a materialused generally, for usual manufacturing quality and under usual workingconditions.

It is noted that in the calculation formula for the basic rated life,only the effect of the bearing load on the bearing life is taken intoconsideration. In view of the above, the result of the calculationformula for the basic rated life is greatly different from the result oflife in the market at present. This is because the fatigue life has alsobeen improved by the improvement in the bearing steel materials, and theeffect of the lubricant film thickness at the contact portion between abearing ring and a rolling element on the fatigue life has been analyzedby a study on the theory of elastic fluid lubrication in recent years. Acorrection rated life L_(nm) reflecting the effect of them on the lifecalculation formula was proposed as the following formula (2) by using alife correction coefficient a_(xyz) by ISO 281 in February, 2000.L _(nm) =a ₁ ·a _(xyz) ·L ₁₀  (2)

Further, the life correction coefficient a_(xyz) is shown by thefollowing equation (3).a _(xyz) =f(Pu,κ,a _(c))  (3)

The life correction coefficient a_(xyz) is represented as a functionconsidering factors such as fatigue limit load Pu, lubrication state(kinetic viscosity) κ, and environment coefficient (contamination degreeof lubricant) a_(c). Further, a₁ is a reliability coefficient which isdescribed in the following Table 1 and it takes a lower value as thereliability is improved.

TABLE 1 Reliability % L_(na) a₁ 90 L_(10a) 1 95 L_(5a) 0.62 96 L_(4a)0.53 97 L_(3a) 0.44 98 L_(2a) 0.33 99 L_(1a) 0.21

However, among the variables representing the life correctioncoefficient a_(xyz), the fatigue limit load Pu and the lubrication state(kinetic viscosity) κ are considered quantifiable. However, while theweight, size, shape and substance of foreign substance are consideredfor the contamination degree a_(c) of the lubricant, they are notquantitatively evaluated but merely represent the environmentambiguously. This has resulted in a problem that the life can not bepredicted at high accuracy according to the formula (2).

The present invention has been achieved taking into considerationfactors of the prior art which had not theretofore been apparent and itis an object thereof to provide a life predicting method for a rollingbearing capable of predicting the life at a high accuracy according tothe formula (2) for calculating a correction rated life, a lifepredicting device, a rolling bearing selecting device using the lifepredicting device, a program therefor and an environment coefficientdetermining method.

SUMMARY OF THE INVENTION

In one embodiment of the bearing life predicting method for a rollingbearing according to the present invention, a basic dynamic rated load Cand a basic static rated load C₀ can be calculated, wherein thecorrection rated life L_(nm) of a rolling bearing at a reliabilitycoefficient a₁ is calculated according to:L _(nm) =a ₁ ×a _(xyz)×(C/P)^(p)a_(xyz)∝f(α)where P represents an equivalent load, p represents a load index,a_(xyz) represents a life correction coefficient, and α represents aratio between a typical dimension for a portion of a bearing to be incontact with a mixed foreign substance and a characteristic quantityshowing the size of the mixed foreign substance.

Thus, the life correction coefficient a_(xyz) can be set in accordancewith the characteristic quantity showing the size of the mixed foreignsubstance and, further, since the value α for the ratio thereof with thetypical dimension for the portion of the bearing in contact with themixed foreign substance is used for the setting, the life correctioncoefficient a_(xyz) can be set in accordance with the mixed foreignsubstance not depending on the size of the bearing.

In a further aspect of the invention, the ratio α is calculatedaccording to:α=d/√ S

where √ S represents the typical dimension assuming a typical diameterof the mixed foreign substance as d, and a contact ellipse area in thebearing as S.

Thus, the value α for the ratio is determined by using a contact ellipsearea in the bearing and the life correction coefficient a_(xyz) can beset according to the determined value α for the ratio.

Furthermore, the function f is determined based on an empirical formulaobtained by mixing the foreign substance having different characteristicquantities with respect to the size, respectively.

Thus, since the life correction coefficient a_(xyz) can be obtainedbased on the experimental formula obtained previously by the value α forthe ratio, the life can be predicted at a higher accuracy.

Still further, the function f has a viscosity ratio κ of a lubricant, afatigue limit load Pu and a contamination degree coefficient a_(c) asvariables, and the contamination a_(c) has the value α for the ratio asa variable.

Thus, the present invention is applicable also in a case of determiningthe correction rated life based on the life correction coefficienta_(xyz) using the viscosity ratio κ of the lubricant, the fatigue limitload Pu and the contamination degree coefficient a_(c) as the variablesproposed by ISO 281 in February, 2000.

A further aspect of the present invention is a life predicting devicefor a rolling bearing for conducting life prediction of a rollingbearing such that a basic dynamic rated load C and a basic static ratedload C₀ can be calculated, comprising a specification informationinputting means for inputting specification information containing abasic dynamic rated load C and a basic static rated load C₀ of therolling bearing, a dynamic equivalent load computation means forcomputing a dynamic equivalent load based on the specificationinformation inputted by the specification information inputting means, areliability setting means for setting a reliability coefficient, atypical dimension determining means for determining a typical dimensionfor a portion of a bearing in contact with mixed foreign substance, amixed foreign substance characteristic quantity inputting means forinputting a characteristic quantity showing the size of the mixedforeign substance, a ratio computing means for computing the value forthe ratio between the typical dimension and the characteristic quantity,a life correction coefficient setting means for setting a lifecorrection coefficient based on the value for the ratio, and a bearinglife computation means for computing the bearing life based on thereliability coefficient, the life correction coefficient, the basicdynamic rated load, the dynamic equivalent load and the load index.

Further, the life predicting device for a rolling bearing according tothe present invention inputs specification information by aspecification information inputting means, sets a reliabilitycoefficient by a reliability setting means, determines a typicaldimension by a typical dimension determining means, inputting acharacteristic quantity showing the size of the mixed foreign substanceby a mixed foreign substance characteristic quantity inputting means,determining the value α for the ratio between the typical dimension andthe characteristic quantity by a ratio computing means, thereby settinga life correction coefficient a_(xyz) by computation for:a_(xyz)∝f(α)by a life correction coefficient setting means, and computing thebearing life L_(nm) by computation ofL _(nm) =a ₁ ×a _(xyz)×(C/P)^(p)

based on the reliability coefficient a_(xyz), the life correctioncoefficient a₁, the basic dynamic rated load C, the dynamic equivalentload P, and the load index p.

Further, a life predicting device for a rolling bearing according to thepresent invention has a feature for conducting life prediction of arolling bearing specified such that a basic dynamic rated load C and abasic static rated load C₀ can be calculated, comprising a specificationinformation inputting means for inputting specification informationcontaining a basic dynamic rated load C and a basic static rated load C₀of the rolling bearing, a dynamic equivalent load computation means forcomputing a dynamic equivalent load based on the specificationinformation inputted by the specification information inputting means, areliability setting means for setting a reliability coefficient, atypical dimension determining means for determining a typical dimensionfor a portion of a bearing in contact with mixed foreign substance, amixed foreign substance characteristic quantity inputting means forinputting a characteristic quantity showing the size of the mixedforeign substance, a ratio computing means for computing the value forthe ratio between the typical dimension and the characteristic quantity,a life correction coefficient setting means for setting a lifecorrection coefficient based on the value for the ratio, a bearing lifecomputation means for computing the bearing life based on thereliability coefficient, the life correction coefficient, the basicdynamic rated load, the dynamic equivalent load and the load index, anda re-computation judging means whether re-calculation is necessary ornot for matching a desired life in a case where the result ofcomputation by the bearing life computation means does not correspond tothe desired life. The bearing life predicting device for the rollingbearing judges, when the result of computation by the bearing lifecomputation means does not correspond to a desired life, whetherre-calculation is necessary or not for satisfying the desired life bythe re-computation judging means and, in a case where re-calculation isnecessary, conducts re-calculation by selecting, for example, change ofthe rolling bearing number to a greater one or change of the mixedforeign substance diameter thereby deciding a rolling bearing that cansatisfy the desired life.

The life predicting device for the rolling bearing can determine thevalue α for the ratio using the contact ellipse area in the bearing andcan set the life correction coefficient a_(xyz) by the value α for theratio.

Further, it has feature in that the life correction coefficient settingmeans sets a life correction coefficient obtained by substituting thevalue for the ratio in the empirical formula obtained by mixing theforeign substance having different characteristic quantitiesrespectively with respect to the size in the bearing.

Since the life correction coefficient a_(xyz) can be obtained based onthe empirical formula previously obtained by the value α for the ratio,the life predicting device for the rolling bearing can predict life at ahigher accuracy.

Further, it has a feature in that the life correction coefficientsetting means sets the life correction coefficient with reference to aviscosity ratio of a lubricant, a fatigue limit load, and acontamination degree coefficient which changes depending on the valuefor the ratio.

The life predicting device for the rolling bearing is applicable also ina case of determining the correction rated life based on the lifecorrection coefficient a_(xyz) using the viscosity ratio κ of thelubricant, the fatigue limit load Pu, and the contamination degreecoefficient a_(x) as variants proposed by ISO 281 in February, 2000.

Further, a rolling bearing selecting device using a life predictingdevice for a rolling bearing comprises a bearing species inputting meansfor inputting a bearing species desired by a user, a specificationinformation inputting means for inputting necessary specificationinformation other than the required specification information requiredby the user from necessary specification information containing a basicdynamic rated load C and a basic static rated load C₀ of the rollingbearing, a specification information assuming means for comparing therequired specification information inputted by the specificationinformation inputting means and the necessary specification informationthereby assuming the not-inputted specification information, a lifepredicting device for the rolling bearing conducting bearing lifepredicting computation based on the specification information inputtedby the specification information inputting means and the specificationinformation assumed by the specification information assuming means, ajudging means for judging whether the result of computation by the lifepredicting device can satisfy the specification information inputted bythe specification information inputting means or not, a specificationinformation presenting means for presenting the specificationinformation set by the specification information assuming means when theresult of the judgment by the judging means can satisfy thespecification information, and a re-computing means for changing thespecification information assumed by the specification informationassuming means and conducting re-computation by the life predictingdevice for the rolling bearing when the result of the judgment of thejudging means can not satisfy the specification information.

In the rolling bearing selecting device using the life predicting devicefor the rolling bearing, a bearing type such as a ball bearing, a rollerbearing, a radial bearing, a thrust bearing or the like is inputted bythe bearing species inputting means and, when a user intends to know anyone of the optimal bearing, the optimal operation condition and the lifepredicting time, and inputs the remaining two required items ofspecification information by the specification information inputtingmeans, the specification information assuming means assumed any one ofthe optimal bearing, the optimal operation condition and the lifepredicting time, and conducts the predicting life computation based onthe required specification information and the assumed information. Forexample, in a case where the optimal operation condition is intended tobe known and when the name of the bearing to be used and the requiredlife time are inputted, it assumes the load exerting on the bearing, thenumber of rotations of the bearing and the mixed foreign substancediameter respectively, conducts life predicting computation, conductsthe life predicting computation while changing the specificationinformation assumed by the specification information assuming means in acase where the life predicting time does not satisfy the required lifetime and, when the life predicting computation satisfying the requiredlife time is conducted, presents the operation condition as the optimaloperation condition by the specification information presenting means.

Still further, the specification information inputting means, thespecification information assuming means, the life predicting device forthe rolling bearing, the judging means, the specification informationpresenting means and the re-computation means are adapted accessable byway of an internet.

In the rolling bearing selecting device using the life predicting devicefor the rolling bearing, any one of the optimal bearing, the optimaloperation condition, and the life predicting time can be selected easilyat the information terminal owned by the user when the user conductsaccess by way of the internet to the specification information inputtingmeans, the specification information assuming means, the life predictingdevice for the rolling bearing, the judging means, the specificationinformation presenting means and the re-computation means.

The rolling bearing selecting device further comprises a userregistration accepting means for accepting the user registration by wayof the internet, and adapted such that only the user registered by theuser registration accepting means can access by way of the internet tothe specification information inputting means, the specificationinformation assuming means, the life predicting device for rollingbearing, the judging means, the specification information presentingmeans and the re-computation means.

In the rolling bearing selecting device using the life predicting devicefor the rolling bearing, since only the user who is registered by theuser registration accepting means can select any one of the optimalbearing, the optimal operation condition and the life predicting time byway of the internet, the user information can be obtained by the userregistration accepting means.

Since the rolling bearing selecting device using the life predictingdevice for the rolling bearing can select the language to be used in thespecification information inputting means, the specification informationassuming means, the life predicting device for the rolling bearing, thejudging means, the specification information presenting means and there-computation means, the rolling bearing can be selected by using alanguage desired by a user by optionally selecting a language such asJapanese, English, German or French.

Further, the specification information presenting means is adapted toconduct any one of presentation for the life prediction of the rollingbearing, presentation of the optimal bearing and presentation of theoptimal working condition.

The rolling bearing selecting device using the life predicting devicefor the rolling bearing can appropriately present any one of the lifetime, the optimal bearing and the optimal working condition of therolling bearing desired by the user.

Further it comprises a delivery information presenting means presentingat least one of the delivery date or the estimated sum for the rollingbearing based on the specification information presented by thespecification information presenting means.

The rolling bearing selecting device using the life predicting devicefor the rolling bearing can present, when the specification informationpresenting means presents the optimal bearing, the optimal operationcondition and the life predicting time, the delivery time and theestimated sum of the corresponding bearing, so that it is not necessaryfor a user to request the presentation of the delivery time or theestimated sum.

Further, a program according to the present invention has a memorymedium storing a life predicting program for predicting the life of arolling bearing specified such that a basic dynamic rated load C and abasic static rated load C₀ can be calculated, comprising descriptionsfor executing, by a computer, a step of inputting specificationinformation containing the basic dynamic rated load C and the basicstatic rated load C₀ of the rolling bearing, a step of computing adynamic equivalent load based on the specification information, a stepof setting a reliability coefficient, a step of determining a typicaldimension for a portion of the bearing in contact with mixed foreignsubstance, a step of inputting a characteristic quantity indicating thesize of the mixed foreign substance, a step of computing the value forthe ratio between the typical dimension and the characteristic quantity,a step of setting the life correction coefficient based-on the value forthe ratio, and a step of computing the bearing life based on thereliability coefficient, the life correction coefficient, the basicdynamic rated load, the dynamic equivalent load, and the load index.

Still further, the program according to the present invention has amemory medium storing a life predicting program for predicting life of arolling bearing specified such that a basic dynamic rated load C and abasic static rated load C₀ can be calculated, comprising descriptionsfor executing, by a computer, a step of inputting specificationinformation containing the basic dynamic rated load C and the basicstatic rated load C₀ of the rolling bearing, a step of computing adynamic equivalent load based on the specification information, a stepof setting a reliability coefficient, a step of determining a typicaldimension for a portion of the bearing in contact with mixed foreignsubstance, a step of inputting a characteristic quantity indicating thesize of the mixed foreign substance, a step of computing the value forthe ratio between the typical dimension and the characteristic quantity,a step of setting a life correction coefficient based on the value forthe ratio, a step of computing the bearing life based on the reliabilitycoefficient, the life correction coefficient, the basic dynamic ratedload, the dynamic equivalent load, and the load index, and a step ofjudging whether the re-computation for matching a desired life isnecessary or not in a case where the result of computation for thebearing life does not match the desired life.

A program according to the present invention has a memory medium storinga bearing selecting program for selecting a rolling bearing inaccordance with the specification required by a user, comprisingdescriptions for executing, by a computer, a step of inputting a bearingspecies required by a user, a step of inputting necessary specificationinformation other than the required specification information requiredby the user from the necessary specification information containing abasic dynamic rated load C and the basic static rated load C₀ of therolling bearing, a step of comparing the required specificationinformation and the necessary specification information thereby assumingthe not inputted specification information, a step of predicting life byusing the life predicting program according to claim 16 based on therequired specification information and the assumed specificationinformation other than that described above, a step of judging whetherthe result of the life prediction can satisfy the required specificationinformation or not, a step of presenting the assumed specificationinformation as the bearing selection information when the result of thelife prediction can satisfy the required specification information, anda step of changing the assumed specification information in a casewhether the result of the life prediction can not satisfy the requiredspecification information and conducting re-computation by the lifepredicting program.

The environment coefficient determining method according to theinvention determines an environment coefficient for the life correctioncoefficient used in the bearing life calculation, wherein theenvironment coefficient is determined at least by the ratio between atypical dimension for the portion of the bearing in contact with a mixedforeign substance and a characteristic quantity indicating the size ofthe mixed foreign substance.

The life correction coefficient a_(xyz) for the correction rated lifeL_(nm) proposed by ISO 281 in February, 2000 is represented as afunction by taking factors such as the fatigue limit load Pu, thelubrication state (kinetic viscosity) κ, and the environment coefficient(contamination degree of lubricant) a_(c) into consideration. Then, theweight, the size, the shape and the type of the foreign substances aretaken into consideration for the environmental coefficient(contamination degree of lubricant).

That is, according to the environmental coefficient determining method,the environment coefficient (contamination degree of lubricant) a_(c)used for the bearing life calculation is quantitatively evaluated byusing at least the size of the foreign substance among the weight, size,shape and type of the foreign substances, and the evaluation isconducted by using the value α for the ratio with the typical dimensionfor the portion of the bearing in contact with the mixed foreignsubstance, without depending on the size of the bearing.

The value for the ratio is calculated by:α=d/√ Swhere √ S represents the typical dimension assuming a typical diameterof the mixed foreign substance as d, and a contact ellipse area in thebearing as S. Thus, the value α for the ratio is determined by using thecontact ellipse area in the bearing and the environment coefficient(contamination degree of lubricant) a_(c) is determined by thedetermined value α for the ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing an example of a life predicting method ina life predicting device of a first embodiment according to the presentinvention;

FIG. 2 is a characteristic graph showing the result of an experiment fordetermining an empirical formula for obtaining a life correctioncoefficient a_(xyz), for the result at P/C=0.16;

FIG. 3 is a characteristic graph showing the result of an experiment fordetermining an empirical formula for obtaining a life correctioncoefficient a_(xyz), for the result at P/C=0.32;

FIG. 4 is a characteristic graph showing values by the empiricalformula;

FIG. 5 is a view showing the constitution of a life predicting device ofa second embodiment;

FIG. 6 is a block diagram showing an electrical connection relation inthe life predicting device of the second embodiment;

FIG. 7 is an explanatory view showing a screen for a bearing table;

FIG. 8 is a flow chart showing an example of a life predicting method;

FIG. 9 is an explanatory view showing an initial menu screen;

FIG. 10 is a flow chart showing an example of a bearing selectionprocessing method;

FIG. 11 is an explanatory view for a bearing selection screen;

FIG. 12 is a flow chart showing an example of a new life calculationprocessing method;

FIG. 13 is an explanatory view showing a screen for new life calculationformula;

FIG. 14 is an explanatory view showing a screen for the definition of aload coefficient;

FIG. 15 is an explanatory view showing a screen for the explanation of areliability coefficient;

FIG. 16 is a flow chart showing an example of a dynamic equivalent loadcalculation processing method;

FIG. 17 is an explanatory view showing a screen for a dynamic equivalentload;

FIG. 18 is an explanatory view showing a screen for result output;

FIG. 19 is a view showing a constitution of a bearing selecting deviceas an embodiment of the present invention;

FIG. 20 is a flow chart showing an example of a bearing selectingprocessing method executed by a WWW server;

FIG. 21 is an explanatory view showing the screen for the input ofbearing species;

FIG. 22 is an explanatory view showing a screen for the input ofspecification information;

FIG. 23 is a flow chart showing an example of an optimal operationcondition determining processing method of FIG. 20; and

FIG. 24 is a flow chart showing an example of an optimal bearingdetermining processing method of FIG. 20;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are to be described withreference to the drawings.

(1) First Embodiment First Example of a Life Predicting Device

A life predicting device of a first embodiment is an informationprocessing device for predicting the life of a bearing, for example, bya life predicting application software and it is, for example, apersonal computer for predicting the life of a bearing by an applicationsoftware stored in a memory device. FIG. 1 shows a processing method bythe life predicting device.

At first, at step S1, data for the species of a bearing is inputted.Specifically, a basic dynamic rated load C(N), a basic static rated loadC₀(N), an inner diameter d (mm), an outer diameter D (mm) and a width B(mm) are inputted.

Then, at step S2, other data for the bearing are inputted. Specifically,bearing dimensions such as a radius of curvature of groove, a radius ofcurvature of starting surface, a number of balls, a ball diameter (mm),and a clearance (mm) are inputted. Then, at step S3, a reliabilitycoefficient a₁ is selected from the Table 1 described above. Then, atstep S4, data for working conditions of the bearing is inputted.Specifically, a load coefficient f_(w), a radial load F_(r), an axialload F_(a), a number of rotation (min⁻¹) and a use ratio (%) areinputted.

Then, at step S5, a dynamic equivalent load P (N) and an average numberof rotation N (min⁻¹) are determined by properly using the data inputtedin the step described above. The dynamic equivalent load is determinedas described below.

The dynamic equivalent load P is determined according to the followingformula (4) based on the load coefficient f_(w), the radial load F_(r)and the axial load F_(a) inputted at the step S4 and the radialcoefficient X and the axial coefficient Y set based on the specificationinformation:P=X·F _(r) +Y·F _(a)  (4)

The specification table is, for example, the following Table 2.

TABLE 2 $\frac{f_{0}F_{a}}{Cor}$ e   $\frac{F_{a}}{F_{r}} \leqq e$X    Y    $\frac{F_{a}}{F_{r}} > e$ X     Y 0.172 0.19 1 0 0.56 2.300.345 0.22 1 0 0.56 1.99 0.689 0.26 1 0 0.56 1.71 1.03 0.26 1 0 0.561.55 1.38 0.30 1 0 0.56 1.45 2.07 0.34 1 0 0.56 1.31 3.45 0.38 1 0 0.561.15 5.17 0.42 1 0 0.56 1.04 6.89 0.44 1 0 0.56 1.00

According to the Table 2, since the value for f₀·F_(a)/C_(or) can bedetermined if the coefficient f₀, the static rated load C_(or), and theaxial load F_(a) can be determined, the radial coefficient X and theaxial coefficient Y specified therewith are used. On the other hand, theaverage number of rotation is a number of rotation used in the lifecalculation in a case of including plural working conditions, which isan average value for the number of rotations for respective workingconditions.

The dynamic equivalent load P and the average number of rotation N aredetermined as described at step S5, it goes to step S6, and calculates abasic rated life L₁₀ of the existent formula by using the formula (1)based on the determined dynamic equivalent load P and the average numberof rotation N.

On the other hand, at step S7, it calculate a maximum rolling elementload Q_(max) according to the following formula (5) by using the dynamicequivalent load P determined at the step S4.Q _(max) =P/number of balls  (5)

Then, at step S8, it determines a contact ellipse area S (μm²). Forexample, it determines the contact ellipse area S by properly using thedata obtained in the step S8 by using the Herz's elastic contact theory.Then, at step S9, it inputs an actually measured mixed foreign substancediameter d_(debris) (“debris” means “foreign substance”)(μm).

Then, at step S10, it determines the value for the ratio between thecontact ellipse S and the mixed foreign substance diameter d_(debris)obtained at the step S8 and the step S9 (d_(debris)/√ S, hereinafterreferred to as a standardized foreign substance diameter) and, atsucceeding step S11, it determines a life correction coefficient a_(xtz)from the standardized foreign substance diameter (d_(debris)/√ S) Inthis case, the value √ S for the square root of the contact ellipse areaS corresponds to a typical dimension for a portion of the bearing incontact with the mixed foreign substance, the mixed foreign substancediameter d_(debris) (μm) shows the size of the mixed foreign substanceand corresponds to a characteristic quantity, and the standardizedforeign substance diameter (d_(debris)/√ S) corresponds to the value αof the ratio.

The life correction coefficient a_(xyz) is determined based on thestandardized foreign substance diameter (d_(debris)/√ S) previouslydetermined according to an empirical formula. The empirical formula isto be explained with reference to examples.

As test bearings, 9 numbers of 6006, 6206, 6306, 6012, 6212, 6312, 6017,6217, and 6317 by the bearing numbers shown in the following Table 3 areused. Further, a radial load to provide P/C of 0.32 and 0.16 is loaded.The square root (√ S) for the contact ellipse area S calculated at thestep S8 corresponding to the bearing number and two kinds of P/C values(0.32, 0.16) takes each value shown at the right end in Table 3.

TABLE 3 Bearing Inner diameter Outer diameter Width B Basic dynamicrated Radial load √ contact ellipse Number d (mm) D (mm) (mm) P/C load C(kgf) Fr (kgf) area (μm) 6006 30 55 13 0.32 1350 432 1020 0.16 1350 216823 6206 30 62 16 0.32 1980 635 1352 0.16 1980 318 1084 6306 30 72 190.32 2700 870 1663 0.16 2700 435 1334 6012 60 95 18 0.32 3000 960 12340.16 3000 480 978 6212 60 110 22 0.32 5350 1712 1902 0.16 5350 856 15096312 60 130 31 0.32 8350 2672 2619 0.16 8350 1336 2078 6017 85 130 220.32 5050 1616 1572 0.16 5050 808 1248 6217 85 150 28 0.32 8550 27362436 0.16 8550 1368 1934 6317 85 180 41 0.32 13500 4320 3408 0.16 135002160 2704

Further, the experiment is conducted under the following conditions asshown in the following Table 4.

TABLE 4 Condition Name of testing Ball bearing life testing machinemachine (manufactured by NSK Ltd.) Test load P/C = 0.16, 0.32 (2 types)Number of N = 2500 rpm rotation of bearing Test temperature 80° C.Lubricant #68 turbine oil Mixed foreign Hardness HV870, HV500 (2substance kinds) Sizes (average 32(16) μm, 74(53) μm, foreign substance147(110.5) μm diameter) (3 kinds) Quantity 150 ppm, 300 ppm (2 kinds)

As shown in Table 4, the mixed foreign substance is used for twohardnesses (HV 870, HV 500) for three sizes (average foreign substancediameter) of 32 (16) μm, 74 (53) μm, and 147 (110.5) μm and for twoamounts (150 ppm, and 300 ppm) in the experiment. Accordingly,experimental results under 24 conditions, (2 (kinds of P/C)×2 (kinds ofhardness of foreign substance)×3 (kinds of size of foreign substance)×2(kinds of quantity of foreign substance)) can be obtained for onebearing number.

The life test was conducted by providing the test bearings each by thenumber of tens under the conditions (24 kinds of conditions for eachbearing number). The test was interrupted when the vibration value forthe test bearing on a testing machine reached twice the initialvibration value, and the life was judged by confirming the presence orabsence of flaking at the raceway groove surface, and the time theflaking was confirmed was defined as the life.

The test life is defined up to five times of the calculated life of52%-52% use as groove R specified according to JIS (hereinafter referredto as L_(cal)) at the longest and the test is terminated when thelongest time is reached. 52% mentioned herein is a groove to diameterratio of outer and inner rings (r_(e)/D_(a), r_(i)/D_(a)) assuming thediameter of a rolling element as D_(a) and the groove diameters of theouter ring and the inner rings as r_(e) and r_(i).

The actually measured life L_(exp), was determined from a total rotationtime till occurrence of flaking in 10% of 10 test specimens from theside of the shorter life according to the Weibull distribution function(that is, 10% life), and the value was used.

FIG. 2 and FIG. 3 are examples for the result of the life test. In eachof the graphs, the abscissa expresses the standardized foreign substancediameter (d_(debris)/√ S) and the ordinate expresses the life correctioncoefficient a_(xyz). The value for the life correction coefficienta_(xyz) on the ordinate is a value obtained as a ratio between theactually measured life L_(exp) and the calculation life L_(cal)(L_(exp)/L_(cal)) according to the relation of formula (2) assuming thereliability coefficient a₁ as 1.

FIG. 2 shows the result of the life test for the test bearings for 9kinds of bearing numbers (6006, 6206, 6306, 6012, 6212, 6312, 6017, 6217and 6317) under the conditions at a test load: P/C=0.16, with a hardnessof mixed foreign substance of HV 870 and HV 500, the size of foreignsubstance of 32 (16) μm, 74 (53) μm, and 147 (110.5) μm and the quantityof foreign substance of 150 ppm. The basic rated fatigue life under theconditions is: L₁₀=1356.3 (hr).

Further, FIG. 3 shows the result of the life test on the test bearingsfor 9 kinds of bearing numbers described above under the conditions at atest load: P/C=0.32, with the hardness of mixed foreign substance of HV870 and HV 500, the size of foreign substance of 32 (16) μm, 74 (53) μm,and 147 (110.5) μm and the quantity of foreign substance of 150 ppm. Thebasic rated fatigue life under the conditions is: L₁₀=169.5 (hr).

As shown in FIG. 2 and FIG. 3, it can be confirmed that the lifecorrection coefficient a_(xyz) decreases in the manner of an exponentialfunction as the standardized foreign substance diameter (d_(debris)/√ S)increases. According to plural experimental points described above,approximate formulae (6) and (7) can be obtained for each of theconditions: P/C=0.16, and 0.32 as shown in FIG. 4.y=1.0748e^(−43.449) x  (6)y=0.3914e^(−52.427) x  (7)

In the formula (6) and formula (7), x corresponds to the standardizedforeign substance diameter (d_(debris)/√ S), and y corresponds to thelife correction coefficient a_(xyz)). The empirical formula of thefollowing formula (8) is obtained from the formula (6) and the formula(7).a _(xyz)=0.394{(u/0.16)−1}·e ^(−52,427) t+1.0748{2−(u/0.16)}·e^(−43.449) t  (8)in which u is a value for the load P/C exerting on the bearing and t isthe value d_(debris)/√ S described above.

The correction coefficient a_(xyz) is obtained by substituting the valuet (d_(debris)/√ S) and the value e (P/C) as the working conditions inthe formula (8) as the empirical formula showing the relation betweenthe standardized foreign substance diameter (d_(debris)/√ S) and thelife correction coefficient a_(xyz).

In the empirical formula, the test load is determined only for theconditions at P/C=0.16 and 0.32, because they are upper and lower limitvalues of the test load applied usually.

By using the empirical formula described above, the life correctioncoefficient a_(xyz) is determined from the standardized foreignsubstance diameter (d_(debris)/√ S) at step S11.

At the succeeding step S12, a final life L_(obs) (correction rated lifeL_(nm)) is determined by using the basic rated life L₁₀ determined atthe step S6.

As described above, the correction rated life L_(nm) as the lifeprediction value can be obtained by the life predicting device.

According to the life predicting device described above, a user cancalculate the correction rated life L_(nm) by inputting the bearing typesuch as the basic dynamic rated load C (N), the basic static rated loadC₀(N), the inner diameter d (mm), the outer diameter D (mm), and thewidth B (mm) (step S1), inputting the bearing dimension such as theradius of curvature of groove, radius of curvature of starting surface,the number of balls, the ball diameter (mm), and the clearance (mm),inputting the reliability coefficient (a₁) selected with reference toTable 1 (step S3), inputting the data for the bearing working conditionssuch as the load coefficient (f_(w)), the radial load F_(r), the axialload F_(a), the number of rotation (min⁻¹) and the use ratio (%) thestep S4 and then inputting the actually measured mixed foreign substancediameter d_(debris) measured, for example, by a particle measuringinstrument (step S9), by using the life predicting device based on theinputted data described above.

Then, in the life predicting device, since the life correctioncoefficient a_(xyz) is determined by the empirical formula used in thestep S11 described above while taking the characteristic quantityshowing the size of the foreign substance into consideration, the lifeprediction obtained based on the life correction coefficient a_(xyz) isdetermined properly while reflecting the characteristic of the mixedforeign substance.

Accordingly, since the quantitative evaluation is made while consideringthe size and the shape of the mixed foreign substance by the lifecorrection coefficient a_(xyz), the life predicting device can providethe bearing life obtained according to the formula (2) above aspredicted at a high accuracy.

In the processings described above, the processings at the step S1, thestep S2, and the step S4 correspond to the specification informationinputting means, the processing at the step S3 corresponds to thereliability setting means, the processing at the step S5 corresponds tothe dynamic equivalent load computation means, the processings at thestep S7 and the step S8 correspond to the typical dimension determiningmeans, the processing at the step S9 corresponds to the mixed foreignsubstance characteristic quantity inputting means, the step S10corresponds to the ratio computation means, the processing at the stepS11 corresponds to the life correction coefficient setting means, andthe processings at the step S6 and the step S12 correspond to thebearing life computation means.

(2) Second Embodiment Second Example of a Life Predicting Device

Then, a life predicting device of a second embodiment is to bedescribed.

A life predicting device of the second embodiment is, as shown in FIG.5, a personal computer 1 comprising a computer main body 2, a display 3which is a liquid crystal display or a CRT connected therewith, a keyboard 4, a mouse 5 and a printer 6 connected with the computer main body2.

The internal circuit of the computer main body 2, as shown in FIG. 6,comprises a central processing unit 11, a memory device 13 such as ROMand RAM connected to the central processing unit 11 by way of a systembus 12, a display controller 14 for connecting the display 3 to thesystem bus 12, a key board interface 15 for connecting the key board 4to the system bus 12, a mouse interface 16 for connecting the mouse 5 tothe system bus 12, an input/output interface 17 for connecting theprinter 6 to the system bus 12, and a hard disk 19 connected by way of ahard disk controller 18 to the system bus 12.

In this case, an operating system is accommodated in the hard disk 19,and a life predicting application software for predicting the life of arolling bearing and an electronic catalog storing the specificationinformation of rolling bearings are also accommodated.

Further, as shown in FIG. 7, the electronic catalog stores specificationinformation such as bearing species, bearing number, main dimension, andbasic dynamic rated load C. The electronic catalog may also furtherstore information such as a basic static rated load C₀, a coefficientf₀, an allowable number of rotation, a radial coefficient X and an axialcoefficient Y. In this case, the basic static load coefficient C₀, thecoefficient f₀, the allowable number of rotation, the radial coefficientX and the axial coefficient Y can be seen by scrolling the screen by themanipulation to the mouse 5 and the like.

Further, the life predicting application software executes predeterminedcomputation based on the input specification information by utilizingthe table calculation application software to conduct life predictingprocessing of a rolling bearing.

In the life predicting processing, as shown in FIG. 8, an initial menuscreen is displayed at first at step S21.

The initial menu screen displays, as shown in FIG. 9, functions storedin the application software selectably, which displays a bearing choiceselection area A1, a new life calculation formula selection area A2, abearing life calculation formula (existent formula) selection area A3, aproduct introduction selection area A4, and an end button 21.

Then, it goes to step S22, and judges whether the bearing choiceselection area A1 is selected or not by the mouse 5 or the key board 4.In a case it is selected, it goes to step S22 a, executes the bearingselection processing to be described later and then ends the processing.In a case the bearing choice selection area A1 is not selected, it goesto step S23.

At step S23, it judges whether the new life calculation formulaselection area A2 is selected or not and, if it is selected, it goes tostep S23 a, executes a new life calculation processing described laterand then ends the processing. If the new life calculation formulaselection area A2 is not selected, it goes to step S24.

At step S24, it judges whether the bearing life calculation formula(existent formula) selection area A3 is selected or not by the mouse 5or the key board. In a case where it is selected, it goes to step S24 a,calculates the bearing life L₁₀ by the existent formula in accordancewith the formula (1) described above and then ends the processing. Ifthe bearing life calculation formula (existent formula) selection areaA3 is not selected, it goes to step S25.

At step S25, it judges whether the product introduction selection areaA4 is selected or not by the mouse 5 or the keyboard 4. If it isselected, it goes to step S25 a, executes the product introductionprocessing of displaying the product introduction information previouslystored in the hard disk 19 on the display 3 and then ends theprocessing. If the product introduction selection area A4 is notselected, it goes to step S26.

At step S26, it judges whether the end button 21 is selected or not bythe mouse 5 or the key board 4 or not and, if the end button 21 isselected, it ends the life predicting processing as it is. If the endbutton 21 is not selected, it returns to the step S22.

In the bearing selection processing at step S22 a, as shown in FIG. 10,it at first displays at step S31 a bearing selection screen shown inFIG. 11 on the display 3.

The selection screen displays, as shown in FIG. 11 displays a retrievearea 22 retrieving from a bearing table, a retrieve area 23 retrievingfrom the bearing number, a menu button 24 for displaying the inputtedspecification information of the rolling bearing and an end button 24.The retrieve area 22 displays text input areas 22 a to 22 c forinputting minimum values and maximum values of the inner diameter d, theouter diameter D, and the width (height) B (T), a deep groove ballbearing selection button 22 d, an angular ball bearing selection button22 e, s self-aligning ball bearing selection button 22 f, a singledirection thrust ball bearing selection button 22 g, a cylindricalroller bearing selection button 22 h, a tapered roller bearing selectionbutton 22 i, a self-aligning roller bearing selection button 22 j and athrust roller bearing selection button 22 k for selecting bearingspecies. Further, the retrieve area 23 displays a text input box 23 afor inputting the bearing number and a reference button 23 b displayinga list of bearing numbers.

Then, it goes to step S32 and judges whether the input for the innerdiameter d, the outer diameter D, and the width (height) B (T) has beencompleted and selection for the bearing type has been ended or not inthe case of retrieving from the bearing table, or whether the input ofthe bearing number has been ended or not in the case of retrieving fromthe bearing number and waits for the end of the input if one of them hasnot yet been ended till the end of the input. If the input has beenended, it goes to step S33 and judges whether this is the retrieval fromthe bearing table or not and, if it is retrieved from the bearing table,it goes to step S34, retrieves the electronic catalog based on the innerdiameter d, the outer diameter D, the width (height) B (T), and thebearing species, displays the bearing table screen shown in FIG. 7 fordisplaying the corresponding specification information and then goes tostep S36. If retrieval is selected from the bearing number, it goes tostep S35, retrieves the electronic catalog based on the bearing numberinputted to the text input box 23 a, displays the bearing table screwshown in FIG. 7 for displaying the corresponding specificationinformation and then goes to step S36.

In this case, the bearing table screen displays, as shown in FIG. 7, aspecification information display area 31 for displaying thecorresponding specification information of the electronic catalog, anexistent formula life calculate button 32, a new life calculate button33 according to the invention, a return button 33, a menu button 36, andan end button 37.

At step S36, it selects a desired bearing number and then judges whetherthe existent formula life calculate button 32 is selected or not and, ifthe existent life calculate button 32 is selected, it goes to step S36a, conducts computation of the formula (1) to execute the existentformula life calculation processing of calculating the basic rated lifeL₁₀ and then ends the processing. In a case if the existent lifecalculate button 32 is not selected, it goes to step S37.

At step S37, it selects a desired bearing number, then judges whetherthe new life calculate button 33 is selected or not and, if the new lifecalculate button 33 is selected, it goes to step S 37 b, conducts newlife calculation processing to be described later and ends theprocessing. In a case if the new life calculate button 33 is notselected, it goes to step S38.

At step S38, it judges whether the menu button 36 is selected or notand, if the menu button 36 is selected, it goes to step S38 a, actuatesthe initial menu display processing shown in FIG. 8 and then ends theprocessing. In a case if the menu button 36 is not selected, it goes tostep S39.

At step S39, it judges whether the end button 37 is selected or not and,if the button is selected, it ends the life calculation processing as itis. In a case if the end button 37 is not selected, it goes to step S40and judges whether the return button 35 is selected or not and, if thebutton is selected, it returns to the step S31. In a case if the returnbutton 35 is not selected, it returns to the step S36.

In the new life calculation processing at the steps S23 a and S37 a, itat first displays at step S51, as shown in FIG. 12, displays a new lifecalculation screen shown in FIG. 13.

Further, the new life calculation screen has a display area 41 fordisplaying predetermined items, and a calculation execute button 42, aread button 43, a preserve button 44, an initialize button 45, a returnbutton 46 and a menu button 47 arranged below the display area 41.

In this case, the display area 41 displays the life calculation formulaof the formula (2) in a heading portion, and has a combo box 51 forselecting the bearing type, a text box 52 for inputting the bearingnumber, a text box 53 for inputting a bearing dynamic rated load C, atext box 54 for inputting a bearing static rated load C₀, a text box 55for inputting a bearing inner diameter d, a text box 56 for inputting abearing outer diameter D, a text box 57 for displaying a bearing dynamicequivalent load P, a text box 57 for inputting a load coefficient f_(w),a combo box 59 for selecting a reliability coefficient a₁, a dynamicequivalent load calculate button 60 for indicating the calculation ofthe dynamic equivalent load, a text box 60 for inputting the radius ofcurvature of groove, a text box 61 for inputting the radius of curvatureof raceway surface, a text box 62 for inputting the number of balls, thetext box 63 for inputting the ball diameter, a text box 64 for inputtingthe clearance, a text box 65 for inputting the mixed foreign substancediameter, a dynamic equivalent load calculate button 66, a combo box 67for selecting the specification of the bearing material, and a selectbutton 68 for selecting the absence or presence of a particular inputfor the fatigue limit load Pu. Then, the text box 58 for the loadcoefficient f_(w) displays “1.0”, the combo box 59 for the reliabilitycoefficient a₁ displays “90”, and the combo box 67 for the specificationof the bearing material displays “high carbon chromium bearing steel(SUJ2Z, SUJ3Z)” as default values.

Then, it goes to step S52 and judges whether the read button 43 isselected or not and directly goes to step S58 if the button is notselected. In a case where the read button 43 is selected, it goes tostep S58 and successively displays the specification information for therolling bearing of the bearing number selected in the bearing table ofFIG. 7 in the order of the combo box 51 and the text box 52. When itdisplays the bearing outer diameter D in the text box 56, it goes tostep S54 and displays the screen for the definition of the loadcoefficient having a display area 61 for displaying the description forthe definition of the load constant and a close button 62 shown in FIG.14. Then, it goes to step S55, and judges whether the close button 62 isselected or not and, if the button is not selected, it waits till theselection and goes to step S56 when it is selected.

Then, at step S56, it displays a screen for the explanation of thereliability coefficient having a display area 63 for displaying asentence for the reliability coefficient and a close button 64 shown inFIG. 15, then goes to step S57 and judges whether the close button 64 isselected or not. In a case if the button is not selected, it waits tillselection and, if the close button 64 is selected, it goes to step S58.

At step S58, it judges whether the dynamic equivalent load calculatebutton 66 is selected or not and, if it is selected, it goes to stepS59, conducts the dynamic equivalent load calculation described laterand then goes to step S60. In a case if the dynamic equivalent loadcalculate button 66 is not selected, it goes to step S60 as it is.

At step S60, it judges whether the calculate execute button 42 isselected or not and, if the calculate execute button 42 is selected, itgoes to step S61 and judges whether the data necessary for calculationhas already been inputted or not. The data necessary for the calculationis the data to be inputted to the text box displayed in the display area41 described above, which is the data necessary for determining thecorrection rated life L_(nm).

If not all the data necessary for the calculation are inputted, it goesto step S62, displays message information for promoting the completionof the input of the data necessary for the calculation and then returnsto the step S61 and stays in a data input waiting state. On the otherhand, when all the data necessary for the calculation have beeninputted, it goes to step S63.

At step S63, it judges whether the calculation for the dynamicequivalent load P is ended or not and, if it is not ended, it goes tostep S64, displays message information for promoting the precedentcompletion for the calculation of the dynamic equivalent load Pprecedingly, and then returns to the step S58. If the calculation forthe dynamic equivalent load P is completed, it goes to step S65 andcomputes the formula (2) to conduct life calculation processing forcalculating the correction rated life

That is, it determines the maximum rolling element load Q_(max) based onthe formula (5) from the dynamic equivalent P determined at the step S59(processing at step S7 shown in FIG. 1) and successively determines thecontact ellipse area S (μm²) (processing at step S8 shown in FIG. 1).Then, it calculates the standardized foreign substance diameter(d_(debris)/√ S) based on the contact ellipse area S (μm²) and the mixedforeign substance diameter (d_(debris)) inputted to the text box 65, andcalculates the life correction coefficient a_(xyz) based on the formula(8) as the previously obtained empirical formula (8). On the other hand,it calculates the basic rated life L₁₀ based on the formula (1) from thedynamic equivalent load P. Then, it calculates the correction rated lifeL_(nm) according to the formula (2) based on the calculated lifecorrection coefficient a_(xyz) and the basic rated life L₁₀.

After conducting the life calculation processing of calculating thecorrection rated life L_(nm), it ends the processing and goes to stepS60 in a case if the result of judgment at the step S60 showing that thecalculation execute button 42 is not selected, it goes to step S66 andjudges whether the preserve button 44 is selected or not. In a case ifthe preserve button 44 is selected, it goes to step S67 and preservesdata displayed on each boxes 51 to 65 at that instance and then returnsto the step S60. In a case if the preserve button 40 is not selected, itgoes to step S68.

At step S68, it judges whether the initialize button 45 is selected ornot and, if the initialize button 45 is selected, it goes to S69,deletes the displayed data and then returns to the step S52. In a caseif the initialize button 45 is not selected, it goes to step S70 andjudges whether the return button 46 is selected or not. In a case if thereturn button 46 is selected, it returns to step S33 in the bearingselection processing in FIG. 10. In a case where the return button 46 isnot selected, it goes to step S71 and judges where the menu button 40 isselected or not. In a case if the menu button 47 is selected, it goes tostep S72, starts the initial menu display processing and ends theprocessing. In a case if the menu button 47 is not selected, it returnsto the step S58.

The dynamic equivalent load calculation processing executed at the stepS59 by the selection of the dynamic equivalent calculate button 66 atthe step 58 displays, specifically, as shown in FIG. 16, a dynamicequivalent load calculation screen shown in FIG. 17 at first at stepS81.

The dynamic equivalent load calculation screen has a display area 71 forindicating predetermined items and a calculation execute button 72, aresult reflect button 73, a return button 74 and a menu button 75displayed below the display area 71.

The display area 71 has a combo box 76 for selectively displaying thebearing type, a text box 77 for displaying the bearing number, a textbox 78 for inputting the radial load fr of working condition, a text box79 for inputting an axial load fa, a text box 80 for inputting thenumber of rotation, a text box 81 for inputting the use condition ratio,an additional input button 82, a text box 83 for displaying the dynamicequivalent load P and a text box 84 displaying the average number ofrotation N.

Then, it goes to step S82, judges whether the calculation execute button72 is selected or not and, in a case if the calculation execute button72 is selected, it goes to step S83, calculates the dynamic equivalent Pby computing the formula (4) based on the radial load F_(r) and theaxial load F_(a) inputted to the text boxes 78 and 79, the radialcoefficient X and the axial coefficient Y set by the specificationinformation, and the load coefficient f_(w) set on the new lifecalculation screen in FIG. 13, displays the calculated dynamicequivalent load P on the text box 83 and then goes to step S84.

At step S84, it judges whether the result reflect button 73 is selectedor not and, in a case if the result reflect button 73 is selected, itgoes to step S85, reflects the calculated dynamic equivalent load P inthe text box 57 for the dynamic equivalent load in the new lifecalculation formula screen in FIG. 13, then goes to step S86, closes thedynamic equivalent load calculation screen in FIG. 17, actuating the newlife calculation screen in FIG. 13 and then ends the processing.

Further, in a case if the calculation execute button 72 is selected atstep S82, and if the result reflect button 73 is not selected at thestep S84, it goes to step S87 and judges whether the return button 74 isselected or not. In a case if the return button 70 is selected, it goesto step S86, re-displays the new life calculation screen of FIG. 13 andends the processing. In a case if the return button 74 is not selected,it goes to step S88 and judges whether the menu button 75 is selected ornot. In a case if the menu button 75 is selected, it goes to step S89,activates the initial menu display processing the FIG. 8 and then endsthe processing. In a case if the menu button 75 is not selected, itreturns to the step S82.

The result of various calculations determined at the step S65 aredisplayed as the result output screen shown in FIG. 18.

The result output screen has a display area 91 for displayingpredetermined items, and a print button 92, a return button 93 and menubutton 94 arranged below the display area 91. The display area 91comprises a text box 95 for displaying a bearing type, a text box 96 fordisplaying the bearing number, a text box 97 for displaying the bearingdynamic rated load, a text box 98 for displaying the bearing staticrated load, a text box 99 for displaying the bearing dynamic equivalentload, a text box 100 for displaying the number of rotation, a text box101 for displaying the contact ellipse area S, a text box 102 fordisplaying the standardized foreign substance diameter (d_(debris)/√ S),a text box 103 for displaying the reliability coefficient a₁, a text box104 for displaying a life correction coefficient a_(xyz), a text box 105for displaying the basic rated life L₁₀ and a text box 106 fordisplaying the correction rated life L_(nm) of the rolling bearing.

The shows processings attained by the life predicting device of thesecond embodiment. The following processings are conducted by a user'soperations.

Now assuming that the life of a deep groove ball bearing having, forexample, a bearing number of “6206” is to be predicted. At first, apower source for the computer main body is turned on to actuate theoperating system and then the life predicting application software isstarted.

Thus, execution for the life predicting processing for the rollingbearing shown in FIG. 8 is started, and the initial menu screen shown inFIG. 9 is at first displayed. In the initial menu screen, when theselection area A1 for the choice of bearing is clicked, for example, bythe mouse 5, the screen for the selection of the bearing shown in FIG.11 is displayed. In a case where the bearing is retrieved from thebearing table, at least each of the text boxes 22 a, 22 b, and 22 c forthe inner diameter, the outer diameter and the width are selectedsuccessively by the mouse 5, the desired dimensions “30”, “62”, and “16”each by the milli unit are inputted from the key board 4, and the deepgroove ball bearing select button 22 d is selected.

Thus, the electronic catalog is retrieved and the specificationinformation such as main dimensions d, D, B, r, and basic dynamic ratedload C (also including the basic static rated load C₀, the coefficientf₀, the allowable number of rotation, the radial coefficient X, and theaxial coefficient Y although not illustrated) for the correspondingbearing number “6206” are displayed in outlined characters on thebearing table screen in FIG. 7. Further, also in a case of directlyinputting the bearing number “6206”, the bearing table screen of FIG. 7is also displayed.

In the bearing table screen, when the new calculate button 33 isselected by clicking the mouse 5, the new life calculation formulascreen of FIG. 13 is displayed and, when the read button 43 is clickedon the new life calculation formula screen, specification informationfor the bearing number selected in the bearing table of FIG. 7 areinputted successively. That is, “deep groove ball bearing” is displayedas the bearing type in the combo box 51, “6206” is displayed in the textbox 52 for bearing number, “1980” is displayed in the text box 53 forbearing dynamic rated load C, “30” is displayed in the text box 55 forthe bearing inner diameter d, and “62” is displayed in the text box 56for the bearing outer diameter D.

Then, the definition screen for the load constant shown in FIG. 14 isdisplayed above the new life calculation screen, and the loadcoefficient f_(w) is determined from the operation condition or theplace for use with reference to the definition screen. In this example,the load coefficient f_(w) is defined to “1.0” as a default value so asto be used for example in electromotive machines, machine tools or airconditioning machines in a smooth operation with no impact shocks.

Then, when the close button 62 is selected, the definition screen forthe load coefficient is closed and, instead, the explanatory screen forthe reliability coefficient shown in FIG. 15 is displayed, and thereliability coefficient a₁ is determined with reference to theexplanatory screen for the reliability coefficient. In this example,“100” is determined as the reliability coefficient a₁ by determining thereliability to 90% as the default value.

Then, when the close button 64 is selected by the mouse 5, theexplanatory screen for the reliability coefficient is closed to actuatethe new life calculation screen. In this case, necessary informationsuch as determined load coefficient f_(w), reliability coefficient a₁,radius of curvature for groove, radius of curvature for raceway surface,number of balls, ball diameter, clearance, and mixed foreign substancediameter are inputted to the text box 58 to text box 64 respectively byusing the key board 4. Since the default values are used for the valuesof the load coefficient f₂, and the reliability coefficient a₁ in thisexample, inputting is saved.

In this state, when the dynamic equivalent load calculate button 66 isselected by the mouse 5, the dynamic equivalent 6 calculation screwshown in FIG. 17 is displayed. In the dynamic equivalent loadcalculation screen, the theoretical radial load F_(r) and thetheoretical axial load F_(a) determined from the working conditions areinputted into the text boxes 78 and 79 by using the key board 4, as wellas the number of rotation, for example, “5000” min⁻¹ is inputted intothe text box 80 by using the key board 4. In this case, if pluralworking conditions are present, the additional input button 82 isselected by the mouse 5 and then the theoretical radial load F_(r),theoretical axial load F_(a), the number of rotation N and the workingcondition ratio are inputted by using the key board 4.

In the state where the inputs have been completed, the computation forthe formula (4) is conducted by selecting the calculation execute button72 by the mouse 5 to calculate the dynamic equivalent load P, and theaverage number of rotation N is calculated in a case where the pluralworking conditions are present, and the number of rotation inputted tothe text box 80 is calculated as the number of rotation N in a case ofsingle condition, and the calculated dynamic equivalent load P and theaverage number of rotation N are displayed in the text boxes 83 and 84.

Then, when the reflect button 73 is selected by the mouse 5, the dynamicequivalent load calculation screen is closed and the new lifecalculation formula screen of FIG. 13 is actuated to display thecalculated dynamic equivalent load P and the average number of rotationN in the text boxes 57 and 61. Further, for example, in a case where thecalculated dynamic equivalent load P exceeds 50% of the basic dynamicrated load C or exceeding the basic static rated load C₀, a warningmessage is displayed.

Then, when the calculation execute button 42 is selected by the mouse 5,the maximum rolling element load Q_(max), and the contact ellipse area Sare calculated based on the inputted data, further, the standardizedforeign substance diameter (d_(debris)/√ S) is calculated from thecalculated contact ellipse area S and the inputted mixed foreignsubstance diameter d_(debris), and the life correction coefficienta_(xyz) is calculated based on the empirical formula (8) based on thecalculated standardized foreign substance diameter (d_(debris)/√ S), theformula (2) is calculated based on the life correction coefficienta_(xyz) and the calculated dynamic equivalent load P, and the resultoutput screw shown in FIG. 18 is displayed, to display the contactellipse area S, the standardized foreign substance diameter(d_(debris)/√ S), the reliability coefficient a₁, the life correctioncoefficient a_(xyz), the basic rated life L₁₀ and the correction ratedlife L_(nm) into the text box 141 to text box 146.

When the print button 92 is selected by the mouse 5 and clicked on theresult output screen, all the data displayed on the result output screenare printed by the printer 6.

Then, it is judged as to whether the calculated bearing life can satisfythe bearing life desired by a user or not and the processing is ended ifit is satisfied. However, if the bearing life desired by the user is notsatisfied, the bearing number is changed to make the size of the bearingto be used larger, or the foreign substance mixed diameter is changed orthe like and the correction rated life L_(nm) is calculated again basedthereon to select the rolling bearing that can satisfy the bearing lifedesired by the user.

(3) Third Embodiment Rolling Bearing Selecting Device Using the LifePredicting Device

Then, a rolling bearing selecting device using the life predictingdevice of a third embodiment according to the present invention is to bedescribed.

The rolling bearing selecting device is, as shown in FIG. 19, applied toa WWW (World Wide Web) server 202, which is connected to an internet 200by way of a router 201, in which an electronic catalog for storing abearing selection application software including a life predictingapplication software and specification information for rolling bearingsare stored in the hard disk thereof.

The bearing selection application software executes the rolling bearingselection processing including the life predicting processing forrolling bearings in the life predicting device of the second embodimentdescribed above based on the inputted specification informationutilizing the table calculation application software or the like topresent optimal bearing, optical operation condition and life predictingtime desired by a user.

In the rolling bearing selecting processing, as shown in FIG. 20, it atfirst judges at step S401 whether there is an access from a informationprocessing apparatus such as a personal computer of a user by way of theinternet 200 and, in a case if there is no access from the user, itstands-by till the access arrives. In a case where the access arrivesfrom the user, it goes to step S402 and sends a display information forthe displaying the bearing the selection screen having a languageselection section for selecting Japanese, English, German, French, etc.as the language, then goes to step S403, judges what language isselected, executes the notation processing for the selected language andthen goes to step S404.

At the step S404, it requests for the input of the user's accountinformation and password, sends an input screen information forpromoting the user registration to a user's information processingapparatus in a case where the user is not registered and then goes tostep S405 and judges whether the input of the user's account informationand the password has been conducted or not. In a case if the input forthem has been conducted, it goes to step S409 to be described later andin a case where the input for the user's account information and thepassword is not conducted, it goes to step S406, judges whether the userregistration has been selected or not and if it is not selected, it goesto the step S407, judges whether the user's access is ended or not andreturns to the step S401 in a case where the user's access is ended. Ina case where the user access is not ended, it returns to the step S405.

Further, as the result of judgment at the step S406, if the userregistration is selected, it goes to step S408, executes userregistration processing and then goes to step S409. In the userregistration processing, it sends an input screen information fordisplaying the input screen that inputs full name, company name,division name, electronic mail address or telephone number to the usersinformation processing apparatus and, when predetermined items have beeninputted to the input screen information, issues the user's accountinformation and password, ends the processing and goes to the step S409.

At the step S409, it sends purchase information input screen informationfor inputting the desired bearing delivery date and desired bearing costto the user's information processing apparatus, then goes to step 410,and judges whether the desired delivery date and the desired cost of thebearing have been inputted or not based on the purchase informationinput screen information. When one or both of them has been inputted, itgoes to step S411, stores the inputted desired bearing delivery dateand/or desired cost to a predetermined memory area and then goes to stepS413. In a case if the bearing desired delivery date and the deliverycost are not inputted, it goes to step S412 and judges whether a skipbutton is selected or not. In a case if the step button is not selected,it returns to the step 410 and in a case if the skip button is selected,it goes to step S413.

At step S413, it sends a display information for displaying the bearingspecies display screen shown in FIG. 21 for inputting the bearingspecies to the user's information processing apparatus. The bearingspecies display screen displays a check box 211 for selecting whetherthe bearing is a ball bearing or the roller bearing, a check box 212 forselecting whether the bearing is a radial bearing or a thrust bearing, acheck box 213 for selecting the presence or absence of the designationfor the row, a dropdown box 214 for selecting single row, double row andplural row, a return button 215 and a next button 216, in which thecheck boxes 211 and 212 are set as essential input items.

Then, it goes to step S414 and judges whether the next button 216 isselected or not. In a case if the button is not selected, it goes tostep S415 and judges whether the return button 215 is selected or not.In a case if the button is not selected, it returns to the step S414and, if the button is selected, it returns to the step S409.

Further, as the result of judgment at the step S414, in a case where thenext button 216 is selected, it goes to step S416, and sends the displayinformation for displaying the specification information input screenshown in FIG. 22 to the user's information processing apparatus. Thespecification information input screen has a display area 221 fordisplaying predetermined items, a calculation execute button 222, a readbutton 223, a preserve button 224, an initialize button 225 and a returnbutton 226 arranged below the display area 221.

In this case, the display area 221 comprises a combo box 231 forselecting the bearing type, a text box 232 for inputting the bearingnumber, a text box 233 for inputting the bearing dynamic rated load C, atext box 234 for inputting the bearing static rated load C₀, a text box235 for inputting the bearing inner diameter d, a text box 236 forinputting the bearing outer diameter D, a text box 237 for displayingload P/C exerting on the bearing, a text box 238 for inputting thenumber of rotation, a text box 239 for inputting the mixed foreignsubstance diameter, a text box 240 for inputting the required bearinglife time L_(D) and a combo box 241 for selecting the specification ofthe bearing material. Then, “high carbon chromium bearing steel (SUJ2Z,SUJ3Z)” is displayed as the default value in the combo box 241 for thespecification of the bearing material. Further, by selecting the readbutton 223 in a state of inputting the bearing number into the text box232, the bearing dynamic rated load C, the bearing static rate load C₀,the bearing inner diameter, and the bearing outer diameter correspondingto the bearing number are displayed respectively in the text boxes 233to 236. By selecting the preserve button 224, each of the data stored inthe display area 221 is preserved and, when the initialized button 225is selected, the data in the display region 221 return to the initialstate.

Then, it goes to step S417 and judges whether the calculation executebutton 222 is selected or not and in a case if the calculation executedbutton is not selected, it goes to step S418 and judges whether thereturn button 226 is selected or not. In a case if the return button 226is selected, it goes to the step S413 and, in a case if the returnbutton 226 is not selected, it returns to the step 417.

Further, in a case where the calculation execute button 222 is selectedas a result of judgment at the step S317, it goes to step S419 andjudges whether the bearing number is inputted or not. In a case wherethe bearing number is inputted, it goes to step S420 and judges whetherthe operation condition items of the load P/C exerting on the bearing,the number of rotation of the bearing, the mixed foreign substancediameter and the specification for the bearing material are inputted ornot. In a case if the operation condition items are inputted, it judgesthat the user requests for the bearing life time and goes to step S422and calculates the dynamic equivalent load P, the maximum rollingelement load Q_(max), the contact ellipse area S (μm²), the standardizedforeign substance diameter (d_(debris)/√ S), and the life correctioncoefficient a_(xyz) in the same manner as the processing conducted bythe life predicting device of the first embodiment described above andcalculates the correction rated life L_(nm) based thereon. For thevalues necessary in the course till the correction rated life L_(nm) isobtained and which are not requested for the user to input, generaldefault values are used for instance.

It calculates the correction rated life L_(nm) and then goes to stepS423 to display the correction rated life L_(nm), and sends the displayscreen information for displaying the optimal delivery date and deliverycost of the bearing to the user's information processing apparatus andthen goes to step S424, and judges whether the end button included inthe display screen information is selected or not. In a case if the endbutton is selected, it returns to the step S401 and in a case if the endbutton is not selected, it goes to step S425 and judges whether thereturn button is selected or not. In a case if the return button isselected, it returns to the step S416 and, in a case if the returnbutton is not selected, it returns to step S424.

Further, in a case where the operation condition items are not inputtedas the result of judgment at the step S420, it goes to step S426 andjudges whether the required bearing life time L_(D) is inputted or not.In a case where the required bearing life time L_(D) is not inputted, itgoes to step S427, sends a guidance information for promoting the inputof the operation conditions for the required bearing life time to theuser's information processing apparatus and then returns to the stepS420. In a case if the required bearing life time L_(D) is inputted, itjudges that the user requests for the optimal operation conditions, goesto step 428 and effects the optimal operation condition decidingprocessing.

In the optimal operation condition determining processing, as shown inFIG. 23, it at first goes to step S429 and sets an assumed value as theoperation condition.

The assumed values are set to those values considered appropriate fornecessary values for calculation such as of setting P/C=0.1 as theassumed value for the load exerting on the bearing, setting a value 1/10for the allowable number of rotation as the assumed value for the numberof rotation of the bearing and setting SUJ2 as the assumed value for thebearing material.

Then, it goes to step S430, calculates the dynamic equivalent load P,the maximum rolling element load Q_(max), the contact ellipse area S(μm²), the standardized foreign substance diameter (d_(debris)/√ S), andthe life correction coefficient a_(xyz), in the same manner as theprocessing conducted by the life predicting device of the firstembodiment described above based on each of the assumed values and thebearing dynamic rated load C and the bearing static rated load C₀ basedon the bearing number, calculates the correction rated life L_(nm) basedthereon and then goes to step 431.

At the step S431, it judges whether the calculated correction rated lifeL_(nm) is, for example, within ±10% of the required bearing life timeL_(D). In a case of: L_(D)×0.9≦L_(nm)≦L_(D)×1.1, it judges that theassumed operation conditions are optimal conditions, goes to step S431,sends the display information for the optimal condition display screenfor displaying the optimal operation conditions to a user's informationprocessing device, then conducts the display and sends the displayscreen information for displaying the delivery time and the deliverycost of the optimal bearing to the user's information processing device,then ends the sub-routine processing and goes to the step S424 of FIG.20.

Further, in a case where the result of judgment at the step S431 shows:L_(nm)<L_(D)×0.9 or L_(D)>L_(D)×1.1, it goes to step S433, changes theassumed values for the operation conditions to the previously set nextassumed values and then goes to the step S430.

Now referring again to the FIG. 20, in a case if the result of judgmentat the step S419 shows that the bearing number is not inputted, it goesto step S434, judges whether the operation conditions described aboveare inputted or not. In a case where the operation conditions areinputted, it goes to step 435, and judges whether the required bearinglife time L_(D) is inputted or not. In a case if the required bearinglife time L_(D) is inputted, it judges that the user requires selectionfor the optimal bearing, goes to step 436 and executes the optimalbearing determining processing.

In the optimal bearing determining processing, as shown in FIG. 24, itat first refers to the bearing type at step S437 and assumes the bearingnumber 6206 for the deep groove ball bearing or the bearing number 7206for the angular ball bearing in a case of a standard bearing of largebearing production amount, for example, a radial ball bearing, thebearing number NU206 for the cylindrical roller bearing in a case of theradial roller bearing, or the bearing number HR30206 for the taperedroller bearing in a case of the radial roller bearing, assuming thebearing number 51306 for the thrust ball bearing in the case of thethrust ball bearing, and assuming the bearing number 29420 for thethrust self-aligning roller bearing in a case of the thrust rollerbearing.

Then, it goes to step S438, calculates the dynamic equivalent load P,the maximum rolling element load Q_(max), the contact ellipse area(μm²), the standardized foreign substance diameter (d_(debris)/√ S), andthe life correction coefficient a_(xyz) in the same manner as theprocessing conducted by the life predicting device of the firstembodiment described above based on the assumed bearing number and theoperation conditions, calculates the correction rated life L_(nm) basedon them and then goes to step S439.

At the step S439, it judges whether the calculated correction rated lifeL_(nm) is, for example, within ±10% of the inputted required bearinglife time L_(D) and, in a case of: L_(D)×0.9≦L_(nm)≦L_(D)×1.1, judgesthat the assumed bearing number is the optimal condition, goes to stepS440, displays the optimal bearing number, sends the optimal bearingselection display screen information for displaying the delivery timeand the delivery cost for the optimum bearing to the user's informationprocessing device and then goes to the step S424.

Further, in a case where the result of the judgment at the step S439shows: L_(nm)≦L_(D)×0.9 or L_(m)≧L_(D)×1.1, it goes to step S441,changes the assumed bearing number to a larger or smaller value and thenreturns to the step S438.

Referring again to FIG. 20, in a case where the result of judgment atstep S434 shows that the operation conditions are not inputted, it goesto step S442, sends a guidance information of promoting input of thebearing number or the operation conditions to the user's informationprocessing device and then returns to the step S419. Further, in a casewhere the result of judgement at the step S435 shows that the requiredbearing life time L_(D) is not inputted, it goes to step S443, sends aguidance information of promoting input for the bearing number or therequired bearing life time L_(D) to the user's information processingdevice and then returns to the step S419.

Then, the operation of the rolling bearing selection device is to beexplained.

Now, when a user accesses by way of the internet 200 to the WWW server202, the user registration input screen for inputting the user's accountinformation and password are at first displayed and the bearingselection processing can be executed on the user registration inputscreen in a case of a user already registered. However, in a case of auser who is not yet registered, user registration is conducted byinputting predetermined items on the user registration screen, by whichthe user account information and password are set and the bearingselection processing is executed.

In the bearing selection processing, the bearing species input screenshown in FIG. 21 is displayed, the essential input item, i.e., whetherit is a ball bearing or a roller bearing is selected on the bearingspecies input screen, and it is selected for the radial bearing or thethrust bearing. Since the row designation is an optional selection item,it not necessary for designation.

Then, at the instance the selection for the essential items has beencompleted, when the next button 216 is selected, an input screen forinput of the desired delivery date and the desired cost is displayed andone or both of the desired delivery date and the desired cost areinputted in a case where they are necessary and the screen is skippedwhen they are not necessary.

Then, a specification information input screen shown in FIG. 22 isdisplayed. In a case where the bearing such as a deep groove rollingbearing, an angular ball bearing, a cylindrical roller bearing, aself-aligning roller bearing, or the like is determined on thespecification information input screen and where the correction ratedlife L_(nm) is intended to know for the bearing for which the bearingnumber is determined, at least the load P/C exerting on the bearing, thenumber of rotation of the bearing and the mixed foreign substancediameter as the essential input items are inputted. In a case where themixed foreign substance diameter is not inputted, a general or averageforeign substance diameter is set. Further, in a case where the bearingmaterial is not inputted, SUJ2 is set.

When the input for the operation conditions has been completed and whenthe calculation executed button 222 is selected, it executes the samecomputation as by the life predicting device of the first embodimentdescribed above to calculate the dynamic equivalent load P, the maximumrolling element load Q_(max), the contact ellipse area S (μm²), thestandardized foreign substance diameter (d_(debris)/√ S), and the lifecorrection coefficient a_(xyz), calculates the correction rated lifeL_(nm) based thereon and outputs the calculated correction rated lifeL_(nm) to the display 3 or the printer 6.

Further, in a case where it is intended to know the optimal operationconditions, a bearing number is inputted, and the required bearing lifetime L_(D) is inputted on the specification information input screen ofFIG. 22.

In this case, when the required bearing life time L_(D) is inputted as“50,000 hr” for the bearing number “6306”, for example, and thecalculation execute button 222 is selected, an assumed value P/C=0.1(P=2670N) is set as the load P/C exerting on the load bearing, 5000 rpmis set as the assumed value for the number of rotation of the bearingand a general or average value is set as the assumed value for the mixedforeign substance diameter.

When the same life calculation processing as in the first Example isconducted based on the conditions, concrete values are calculated forthe dynamic equivalent load P, the maximum rolling element load Q_(max),the contact ellipse area S (μ²), the value for (d_(debris)/√ S), and thelife correction coefficient a_(xyz), and a concrete value for thecorrection rated life L_(nm) is calculated based thereon.

Then, the correction rated life L_(nm) and the required bearing lifetime L_(D) are compared and the predicting computation is conductedagain till the correction rated life L_(nm) satisfies the requiredbearing life time L_(D). Then, if it is satisfied, the correction ratedlife L_(nm) and the bearing number are displayed, and an answer screendisplaying the estimated sum and the delivery time for the bearing isdisplayed on the display 3.

(4) Other Embodiments

In the embodiments described above, while description has been made to acase where the life correction coefficient a_(xyz) has only the mixedforeign substance diameter d_(debris) as the variable, but this is notlimitative. for example, computation is conducted for determining thelife correction coefficient a_(xyz) by using variables such as fatiguelimit load Pu, lubrication state (kinetic viscosity) κ and environmentcoefficient (contamination degree of lubricant) a_(c) in accordance withthe proposal of ISO 281 in February, 2000, and the portion for thecomputation processing of the environmental coefficient (contaminationdegree of lubricant) a_(c) is conducted by using the mixed foreignsubstance diameter d_(debris) by the computation described above byapplying the present invention.

Further, in the foregoing embodiment, while description has been made toa case of the ball bearing setting the load index p at 3, this isapplicable also to a roller bearing setting the load index as: p=10/3.This is applicable also in the same manner as in the embodimentdescribed above by determining the contact ellipse area (bearingdimension specification) and working condition (load, average mixedforeign substance diameter, etc.).

Further, in the foregoing embodiments, while the contact ellipse area S(μm²) is determined by using the Herz's elastic contact theory, thecontact ellipse area may be determined by using other theories orempirical formulas.

Further, in the embodiments described above, while the standardizedforeign substance diameter (d_(debris)/√ S) as the standardizedcharacteristic quantity is calculated defining the typical dimension forthe portion of the bearing in contact with the mixed foreign substanceas √ S and the characteristic quantity showing the size of the mixedforeign substance as the diameter d_(debris) thereof and the lifecorrection coefficient a_(xyz) is obtained based on the calculatedstandardized foreign substance diameter (d_(debris)/√ S), this is notlimitative. That is, the life correction coefficient a_(xyz) isobtained, for example, by determining the value α for the ratio usingthe dimension for other portion as the typical dimension for the portionof the bearing to be in contact with the mixed foreign substance orusing other dimension capable of showing the characteristic of theforeign substance as the characteristic quantity of the mixed foreignsubstance thereby obtaining the coefficient according to the determinedvalue α for the ratio.

Further, the standardized foreign substance diameter is defined as adimension value by dividing d_(debris) as the characteristic quantityshowing the size of the mixed foreign substance by √ S as the typicaldimension for the portion in contact with the mixed foreign substance,but this is not limitative. For example, the value α for the ratio maybe a reciprocal of the standardized foreign substance diameter or may bea dimensional value.

Further, in the embodiments described above, while the empirical formula(8) is obtained assuming the evaluation value coefficient as a₁ theempirical formula may be determined also by other evaluation valuecoefficient a₁ in the same manner. In this case, the empirical formulaecan be determined corresponding to plural evaluation value coefficientsa₁ and variation for the selection of empirical formulae usable by theuser can be increased for instance. In this case, in the secondembodiment described above, for example, the user can obtain thecorrection rated life L_(nm) based on the optimal empirical formula inaccordance with the working conditions, etc.

Further, in the embodiment described above, while description has beenmade to a case of executing the program by using a personal computer, itis not limitative but it may be executed also by using other informationprocessing terminals.

Further, in the embodiment described above, while description has beenmade to a case of installing the bearing selection program in the WWWserver 202 but this is not limitative. A bearing selection program maybe installed to a server connected with a local area network and aninformation processing terminal such as a personal computer may takeaccess by way of the local area network server.

Further, in the embodiment described above, while description has beenmade to a case of conducting user registration by the WWW server 202 butit is not limitative. User registration may also be conducted by usingpostal mailing or facsimile.

Further, in the embodiment described above, while description has beenmade to a case of installing the bearing selection application programin the hard disk of the WWW server 202, this is not limitative. It maybe stored into memory medium such as a compact disk (CD) oropto-magnetic disk (MO) other than the hard disk and carried about, ormay be installed to other information processing devices.

According to the present invention, in a life predicting method for arolling bearing for conducting life prediction of a rolling bearingspecified such that a basic dynamic rated load C and a basic staticrated load C₀ can be calculated, since the rated correction life L₁₀ ofa rolling bearing at a reliability factor a₁ is calculated according to:L _(nm) =a ₁ ×a _(xyz)×(C/P)^(p)a_(xyz)∝f(α)where P represents an equivalent load, p represents a load index,a_(xyz) represents a life correction coefficient, and α represents aratio between a typical dimension for a portion of a bearing to be incontact with mixed foreign substance and a characteristic quantityshowing the size of the mixed foreign substance, the live correctedcoefficient a_(xyz) can be set in accordance with the characteristicquantity showing the size of the mixed foreign substance and, further,since the value α for the ratio with respect to the typical dimensionfor the portion of the bearing in contact with the mixed foreignsubstance is used for the setting thereof, the life correctioncoefficient a_(xyz) can be set in accordance with the mixed foreignsubstance not depending on the size of the bearing. Thus, the life canbe predicted at a improved accuracy for the correction rated life.

Further, since the value α for the ratio is calculated according to:α=d/√ Swhere √ S represents the typical dimension assuming a typical diameterof the mixed foreign substance as d, and a contact ellipse area in thebearing as S, the life correction coefficient a_(xyz) can be set bydetermining the value a for the ratio using the contact ellipse area inthe bearing and by the determined value α for the ratio.

Further, since the function f has the viscosity ratio κ of thelubricant, the fatigue limit load Pu and the contamination factor a_(c)as variants, and the contamination a_(c) has the value α for the ratioas a variant, the present application is applicable also in a case ofdetermining the correction rated life based on the life correctioncoefficient a_(xzy) having the lubricant viscosity ratio κ, the fatiguelimit load Pu and the contamination degree coefficient a_(c) as variantsproposed by ISO 281 in February, 2000.

1. A method to predict a life using a computer of a rolling bearinghaving a basic dynamic rated load C and a basic static rated load C₀,comprising calculating the rated correction life L_(nm) of a rollingbearing at a reliability coefficient a₁ according to the relationship:L _(nm) =a ₁ ×a _(xyz)×(C/P)pa_(xyz)∝f(α) where P represents an equivalent load, p represents a loadindex, a_(xyz) represents a life correction coefficient, and αrepresents a ratio between a dimension for a portion of a bearing to bein contact with a mixed foreign substance and a characteristic quantityshowing a size of the mixed foreign substance, wherein the ratio α iscalculated according to the relationship:α=d/√ S where √ S represents the dimension assuming a diameter of themixed foreign substance as d, and a contact ellipse area in the bearingas S, and presenting the calculated rated correction life.
 2. The lifepredicting method according to claim 1, wherein the function f isdetermined based on an empirical formula obtained by mixing foreignsubstances having different characteristic quantities with respect tothe size respectively.
 3. The life predicting method according to claim2, wherein the function f has a viscosity ratio K of a lubricant, afatigue limit load Pu and a contamination coefficient a_(c) asvariables, and the contamination a_(c) has the value α for the ratio asa variable.
 4. A device for predicting a life of a rolling bearinghaving a basic dynamic rated load C and a basic static rated load C₀,comprising: a specification information inputting means for inputtingspecification information containing a basic dynamic rated load C and abasic static rated load C₀ of the rolling bearing; a dynamic equivalentload computation means for computing a dynamic equivalent load based onthe specification information inputted by the specification informationinputting means; a reliability setting means for setting a reliabilitycoefficient; a dimension determining means for determining a dimensionfor a portion of a bearing in contact with mixed foreign substance, amixed foreign substance characteristic quantity inputting means forinputting a characteristic quantity showing the size of the mixedforeign substance; a ratio computing means for computing the value forthe ratio between the dimension and the characteristic quantity; a lifecorrection coefficient setting means for setting a life correctioncoefficient based on the value ratio; a bearing life computation meansfor computing the bearing life based on the reliability coefficient, thelife correction coefficient, the basic dynamic rated load, the dynamicequivalent load and the load index, and means for presenting thecomputed bearing life, wherein the ratio computation means obtains thevalue for the ratio by dividing the diameter of the mixed foreignsubstance with the dimension as the square root for the contact ellipsearea.
 5. A device for predicting a life of a rolling bearing having abasic dynamic rated load C and a basic static rated load C₀, comprising:a specification information inputting means for inputting specificationinformation containing a basic dynamic rated load C and a basic staticrated load C₀ of the rolling bearing; a dynamic equivalent loadcomputation means for computing a dynamic equivalent load based on thespecification information inputted by the specification informationinputting means; a reliability setting means for setting a reliabilitycoefficient; a dimension determining means for determining a dimensionfor a portion of a bearing in contact with mixed foreign substance; amixed foreign substance characteristic quantity inputting means forinputting a characteristic quantity showing a size of the mixed foreignsubstance; a ratio computing means for computing the value for the ratiobetween the dimension and the characteristic quantity; a life correctioncoefficient setting means for setting a life correction coefficientbased on the value ratio; a bearing life computation means for computingthe bearing life based on the reliability coefficient, the lifecorrection coefficient, the basic dynamic rated load, the dynamicequivalent load and the load index; a re-computation judging means forjudging whether the re-computation of aligning a desired life isnecessary or not when the result of computation of the bearing lifecomputation means does not correspond to the desired life, and means forpresenting the computed bearing life, wherein the ratio computationmeans obtains the value for the ratio by dividing the diameter of themixed foreign substance with the dimension as the square root for thecontact ellipse area.
 6. The life predicting device according to claim 4or 5, wherein the life correction coefficient setting means sets a lifecorrection coefficient obtained by substituting the value for the ratioin the empirical formula obtained by mixing the foreign substance havingdifferent characteristic quantities respectively regarding the size inthe bearing.
 7. The life predicting device according to claim 4 or 5,wherein the life correction coefficient setting means sets the lifecorrection coefficient with reference to a viscosity ratio of alubricant, a fatigue limit load and a contamination degree coefficientwhich changes depending on the value for the ratio.
 8. Acomputer-readable memory medium storing a life predicting program forpredicting life of a rolling bearing having a basic dynamic rated load Cand a basic static rated load C₀, comprising descriptions for executing,by a computer: inputting specification information containing the basicdynamic rated load C and the basic static rated load C₀ of the rollingbearing; computing a dynamic equivalent load based on the specificationinformation; determining a dimension for a portion of the bearing incontact with mixed foreign substance; inputting a characteristicquantity indicating a size of the mixed foreign substance; computing thevalue for the ratio between the dimension and the characteristicquantity; setting the life correction coefficient based on the value forthe ratio; computing the bearing life based on the reliabilitycoefficient, the life correction coefficient, the basic dynamic ratedload, the dynamic equivalent load, and a load index, and presenting thecalculated rated correction life, wherein the ratio α is calculatedaccording to the relationship:α=d/√ S where √ S represents the dimension assuming a diameter of themixed foreign substance as d, and a contact ellipse area in the bearingas S.
 9. A computer-readable memory medium storing a life predictingprogram for predicting life of a rolling bearing having a basic dynamicrated load C and a basic static rated load C₀, comprising descriptionsfor executing, by a computer; inputting specification informationcontaining the basic dynamic rated load C and the basic static ratedload C₀ of the rolling bearing; computing a dynamic equivalent loadbased on the specification information; determining a dimension for aportion of the bearing in contact with mixed foreign substance;inputting a characteristic quantity indicating a size of the mixedforeign substance; computing the value for the ratio between thedimension and the characteristic quantity; setting the life correctioncoefficient based on the value for the ratio; and computing the bearinglife based on the reliability coefficient, the life correctioncoefficient, the basic dynamic rated load, the dynamic equivalent loadand the load index; judging whether re-computation for aligning adesired life in a case is necessary or not when the result ofcomputation for the bearing life does not correspond to the desiredlife, and presenting the calculated rated correction life, wherein theratio α is calculated according to the relationship:α=d/√ S where √ S represents the dimension assuming a diameter of themixed foreign substance as d, and a contact ellipse area in the bearingas S.
 10. A computer-readable memory medium storing a bearing selectingprogram for selecting a rolling bearing in accordance with thespecification required by a user, comprising description for executing,by a computer; inputting a bearing species required by a user; inputtingnecessary specification information other than the requiredspecification information required by the user from the necessaryspecification information containing a basic dynamic rated load C and abasic static rated load C₀ of a rolling bearing; comparing the requiredspecification information and the necessary specification informationthereby assuming the not inputted specification information; predictinglife by using the life predicting program according to claim 8 based onthe required specification information and the assumed specificationinformation other than that described above, judging whether the resultof the life prediction can satisfy the required specificationinformation or not; presenting the assumed specification information asthe bearing selection information when the result of the life predictioncan satisfy the required specification information, and changing theassumed specification information in a case when the result of the lifeprediction can not satisfy the required specification information andconducting re-computation by the life predicting program.
 11. Anenvironment coefficient determining method for determining a lifecorrection coefficient used in a roller bearing life prediction, whereinthe environment coefficient is determined at least by a ratio between adimension for a portion of a bearing in contact with a mixed foreignsubstance and a characteristic quantity indicating a size of the mixedforeign substance, wherein the ratio α is calculated according to therelationship:α=d/√ S where √ S represents the dimension assuming a diameter of themixed foreign substance as d, and a contact ellipse area in the bearingas S; and storing the determined environment coefficient for use in aroller bearing life prediction.
 12. The life predicting device accordingto claim 6, wherein the life correction coefficient setting means setsthe life correction coefficient with reference to a viscosity ratio of alubricant, a fatigue limit load and a contamination degree coefficientwhich changes depending on the value for the ratio.